Operational tasks need to be automated. Setting up application environments should always produce the same outcome, including installations, network, and configuration. Container technologies as well as infrastructure as code support this by defining, automating and distributing software installations and configuration. They fulfill the necessity of rebuilding software and systems in a fast and reproducible way.

Infrastructure as code definitions specify the required infrastructure together with all dependencies as part of the application code, kept under version control. This approach supports the ideas behind the DevOps movement. The responsibilities of not only defining the application but also its runtime with all requirements move different teams together. It should be a responsibility of all engineers to deliver quality software that serves a business purpose.

Container technologies such as Docker provides functionality to build, manage, and ship containers in a uniform way. Docker's copy-on-write layered file system enables us to minimize build and publishing times by only re-executing steps that have changed. Java EE zero-dependency applications encourage the use of container technology by separating the application logic from its implementation. The changing layer therefore only contains business code.

Container orchestration frameworks such as Kubernetes manage containers in their life cycle, network, and external configuration. They are responsible to lookup services, provide production readiness such as zero-downtime deployments and scale up and down application instances. Container orchestration supports infrastructure as code definitions, that contain the configuration of the whole runtime environment required by the application.

The 12-factor and cloud native approaches aim to develop modern enterprise applications with minimal time and effort, avoiding software erosion, and supporting Continuous Delivery and cloud platforms. The 12-factor principles target software dependencies, configuration, dependent services, runtime environments, logging and administration processes. Similarly, cloud native applications aim to build enterprise software that works well on cloud platforms, supporting monitoring, resilience, application health, and security. Since these approaches are not bound to a specific technology, they are realizable using Java EE. We have seen the motivations why to follow these principles.

The following chapter will show you how to build productive application development workflows, that are based on container technologies.